The moment of arriving at the back of the cathedral, peering in the window, seeing what was inside, and then realizing - in sheer horror - that I would have to go in there at some point - that chill has stayed with me since first experiencing it 20 odd years ago. The steady competence of moving through the areas suddenly giving way to a panicked thrill as a danger approaches still gets me. Overall, the best most affecting game experience ever, and the Black Parade mod has even elevated it further.